Javascript error in asp.net

Question

I have a calendar control that is hosted on an iframe. I get a javascript error when I click on a date on the calendar. window.top.document.getElementById(..) is null or not an object

The iframe is hosted on another page ConfigSettings.aspx

The code in the calendar control code behind is:

Dim sjscript As String = "<script language=""javascript"" type=""text/javascript"">"
sjscript &= "window.top.document.getElementById('" & HttpContext.Current.Request.QueryString("DateTextID") & "').value = '" & Calendar1.SelectedDate & "';"
sjscript &= "window.top.document.getElementById('" & HttpContext.Current.Request.QueryString("DateTextID") & "1').style.display = 'none';"
sjscript = sjscript & "</script" & ">"
Literal1.Text = sjscript

The html code is:

<input type="text" class="TextBox" id="ToDate" runat="server"/>
    <a href="javascript:ShowCalendar('ToDate1')"><img src="images/Calendar.jpg" border="0" /></a>
                    <iframe src="Calendar.aspx?DateTextID=ToDate" style="display:none; width:200px; height:100px" name="ToDate1" id="ToDate1"></iframe>
<asp:Label runat="server" ID="lblEndTime" Text="End Time:"></asp:Label>

What would be causing the error?

not sure what you mean "same domain"? It is in the same web application — DNR
– DNR, Commented Sep 11, 2011 at 14:50
Does the URL of the iframe have the same domain – e.g. http://www.example.com – as the top level window? — lonesomeday
– lonesomeday, Commented Sep 11, 2011 at 14:51

Pointy · Accepted Answer · 2011-09-11 15:13:55Z

1

You're calling "getElementById()" but not checking to see if it's actually found anything. In other words, if no element on the top page has the "id" value you're looking for, the return value from that function will be null. Your code does not check for that eventuality, however.

edit — to check for null, I'd do something like this:

var dateText = window.top.document.getElementById( ... whatever ... );
if (dateText !== null)
  dateText.value = ... whatever ... ;
else
  alert("cannot find date element");

Another possibility is that "window.top" is not really the right window. If there's another layer of <iframe> involved, then "window.top" would skip over the parent of the <iframe> in the code you posted. You might try changing it to "window.parent" instead of "window.top" and see if that helps.

edited Sep 11, 2011 at 15:13

answered Sep 11, 2011 at 14:58

Pointy

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3 Comments

DNR Over a year ago

But all controls exist on the page, so I don't know why it would not find anything. Can you provide a sample of what the code should look like?

DNR Over a year ago

Thanks for updating your answer, but it does not tell me what is causing the error.

DNR Over a year ago

You EFFING RULE DUDE !!!!!!!!!!!!!!!!!! window.parent worked !! Thanks very much for your help. Your last paragraph hit a home run.

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